Non-Hermitian Topological Magnonics

We demonstrated that chirality diverts thermal flow into the gate. A model was set up to show this effect in a magnetic field, with a magnetic wire at X and a gate. The interaction between the magnetic wire and the magnetic field can be tuned to be chiral when the magnetization is considered. Complications arise because the wire is also a magnet, but when the magnetization between the wire and the film is parallel, the coupling is not chiral. This is evident in the symmetric transmission of spin waves from left to right and right to left, as seen in S12 and S21. However, chirality appears when the magnetization is anti-parallel, leading to asymmetric transmission of spin waves, as shown in S21, S12, and S21.

A surprising effect occurs when the current is turned on. The Y-axis represents the spin current injected into the gate, while the X-axis shows the direction of the film magnetization. The magnetization of the magnetic wire is fixed due to strong coupling. In the anti-parallel configuration with current, spin current is injected into the gate, which does not occur when there is no current. By considering this spin injection, we find that the second law of thermodynamics is not violated.